Dissecting the function of neuropsychiatric disorder-associated genes will greatly enhance our understanding of how specific variants contribute to disease risk. While dCas9 effectors are a novel platform for manipulating gene expression, we report a number of practical limitations that must be considered when designing hiPSC-based studies using this promising new tool. First, gRNA efficacies can vary between genes, individuals, neural cell types, and dCas9 effectors. Second, even the rational design of up to six different gRNAs does not guarantee that a functional gRNA will be validated. Moreover, gRNA efficacy seemed to be independent of dCas9 expression levels (data not shown) and/or antibiotic selection for dCas9 vectors (Figures S2 and S4), suggesting there may not be a quick fix to facilitate transcriptional modulation of particularly intransient genes. Consequently, for hiPSC-based functional studies of neuropsychiatric disease risk genes, we advise that the extent of gRNA gene modulation be validated across each individual, cell type, and effector.
